diff --git a/TODO b/TODO
index e869b72..22a6c9d 100644
--- a/TODO
+++ b/TODO
@@ -18,7 +18,7 @@ code:
 * avoid "force" in coeffs update by using inline functions?
 * should rather use backward Euler in bw_onepole?
 * treat unused variable/function warnings
-* csch for bw_peak bandwidth -> Q
+* csch for bw_peak bandwidth -> Q, inv sqrt ls2 hs2
 * sample rate-constant coeffs? (pan case)
 * pan process with no out: should just reset coeffs?
 * trace calls (debug)